1. FIELD OF THE INVENTION
The present invention relates to a roll-film camera, and more particularly to means for maintenance of requisite tension in film contained therein.
2. DESCRIPTION OF THE PRIOR ART
There is known a type of camera wherein loading or unloading of film is effected only by a dealer or staff of a photographic store, or similar establishment, and not usually by the photographer who actually uses the camera, the camera being supplied as a unit complete with a loaded roll of film to the photographer, who, after exposing all the frames of the roll simply returns the camera to a dealer, for film extraction and development, and purchases, or receives in exchange, another camera containing a fresh roll or film.
Rather than having the object of making it possible to take photographs in almost any conditions, this type of camera usually permits only one or two shutter settings, and is limited to taking photographs in average daylight conditions, but presents the advantages of extreme ease of manipulation and of very low cost, this low cost being made possible by keeping camera constructional elements to a minimum.
This type of camera generally employs film in roll form, rather than in a cassette, for example, film being supplied on a flanged feed spool from which it is gradually unwound, successive film frames being moved to a position for exposure, and then wound onto a flanged take-up spool mounted on and driven by a shaft, which is rotatable upon actuation of a suitable means by a photographer. To keep camera construction as simple as possible, it is desirable to hold film steady in position for exposure simply by tension between spools, but a disadvantage in conventional cameras of this type is that uniform tension in film is not always maintained simply by action of the take-up spool drive shaft, since as more frames of film are exposed the amount of film on the take-up spool increases, with the result that it becomes increasingly difficult to ensure that exposed tilm remains wound up tightly on the take-up shaft and there is a certain amount of slack in the film, which may therefore fail to be moved into a correct alignment for exposure, or when the take-up spool remains unmoved, there is a slight unwinding of film from the take-up shaft, resulting in pressure which actually pushes film backwards and moves a film frame out of a correct exposure position.
Another disadvantage of conventional cameras is that it only needs a very slight misalignment of the drive shaft of the take-up spool for film to spiral on the take-up spool, resulting in film advance becoming difficult or impossible, and film frames not being properly aligned for correct exposure.
It is accordingly an object of the present invention to provide a simple means for ensuring maintenance of tension in a film being wound up in a camera.
It is another object of the invention to provide a film tension maintenance means which also provides support for and ensures maintenance of vertical alignment of a film take-up spool, without a support and drive shaft being necessary.